Analysis fo the role of a novel ovarian protein during oocyte maturation using genetic engineering procedures

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A 80kDa proteinase, follipsin, was isolated from the follicular fluid of porcine ovaries. The enzyme hydrolyzed internal Arg-X bonds of synthetic and natural peptide substrates, and was highly homologous wiht human plasma kallikrein. The enzyme was strongly inhibited by aprotinin, benzamidine, leupeptin, antipain, and diisopropylfluorophosphate, indicating that it is a serine proteinase. It was found that human single-chain tissue-type plasminogen activator was efficiently converted to its two-chain form by the enzyme. The finding suggests the involvement of the serine proteinase in triggering the activation of proteolytic cascade plasminogen activator/plasmin system, that is generally thought to operate in follicle rupture during ovulation.Porcine profollipsin was isolated from the fluid. It was readily activated by trypsin treatment. The study also showed that the follicular fluid of porcine ovary contains a profollipsin-activating enzyme activity.Follicular fluid from human ovaries obtained in in vitro fertilization procedure contained an enzyme similar to porcine follipsin as detected with synthetic, Arg-containing endopeptidase substrates. Purification and characterization studies showed that the enzyme was plasma kallikrein. Plasma kallikrein in association with the proteinase inhibitor alpha 2-macroglobulin was demonstrated to be a predominant form of the enzyme in the fluid, suggesting that the enzyme activity is regulated by the inhibitor. The study also indicated that the plasma kallikrein present in follicular fluid probably comes from the liver.